It is a common requirement to have to make electrical connections to the body surface for measurement of electrical activity originating within the body or to deliver electrical energy into the body. Usually it is necessary to position one or more electrodes in contact with the skin at anatomical locations specific to the intended application. It is also common to devise attachment means such as garments, wraps or braces which incorporate one or more electrodes on their skin facing surface, which locate on the body at target anatomical locations when the garment is worn by the user. Usually such garments incorporate wiring, which connect the electrodes to an electronic module by means of a detachable connector. U.S. Pat. No. 6,885,896 describes such a system where an electronic module interfaces to a holster which is fixed on an internally wired abdominal belt and delivers electrical stimulation signals to the electrodes mounted on the skin facing surface of the belt.
Similar systems can be envisaged for treatment of the knee, back, shoulder etc. and indeed the literature has many examples of garments and braces for different parts of the body incorporating electrodes.
Given a selection of such garments or other attachment means intended for a range of body parts, it is desirable that they would interface to a common electronic module. This would be less costly than having a dedicated electronic module for each garment type. In a typical clinic, it is possible to envisage a selection of single-patient use garments for a range of anatomical sites and a stock of identical electronic controllers which can attach to any garment. The problem with using a common controller for all garments is that the controller would have to be configured by the user or therapist for each garment type prior to use. Furthermore, since a given garment becomes assigned to a particular patient, and the controllers can be swapped or replaced between patients, it is necessary that the controller become personalised to that patient. For this reason it is desirable that the controller can be configured for the type of garment it is connected to and that the treatment for the specific patient can be selected.
The number and size of electrodes on each garment type may be different and the electrical signals applied to each electrode will inevitably be specific to the garment type and the intended treatment. The controller could be manually programmable through data input by the therapist to take account of different garment designs and treatment parameters however this process is error prone.
Traditionally electrotherapy has used electrical generators which have one or more channels, each channel of which has a dedicated pair of electrodes. When the pair of electrodes for a given channel are placed on the body an electrical circuit is completed which allows the therapeutic current to flow in the body between the electrodes of a pair. The path of the current in the body is largely defined by the position of the electrodes on the body. When multiple channels are applied to the body then they are generally isolated so that no current flows between channels. The current pathways on the body are limited to the areas between the individual elements of each pair. Recently the advantage of treating a group of electrodes on the body as an uncommitted array has been recognised. This allows the controller to select which electrode or combination of electrodes is used to source current at any given time and which combination of the remaining electrodes of the array is used as a sink. This allows the controller to set up current pathways between any electrodes of the array, not just between the hardwired pairs of the traditional method. Moreover, it is advantageous to change the electrode groupings during the course of the treatment to, for example, avoid fatiguing the same muscles. The electrode array selection, and the way that selection might be changed with time, is likely to be anatomy specific.
Since garments incorporating arrays of electrodes may be designed for different body parts, it is inevitable that electrode selections to produce anatomically appropriate current pathways will require the selection of different electrode array elements. For example a shoulder brace and a knee brace may both have arrays of 4 electrodes; however different electrode combinations will apply and these combinations are likely to change in different ways for each during treatment. The controller could be designed to accept data input from the therapist to handle this configuration, however this is not a user-friendly solution.
Electrodes in garments may have different surface areas and therefore the current density will vary for a given applied current. It is important therefore that a stimulator be able to calculate and thereby keep below a defined current density limit in order to keep within safety limits. It is therefore necessary to somehow enter data to the controller describing the electrode surface areas. Furthermore, electrodes in electrotherapy garments may have different electrical impedance properties depending on geometry, anatomical location, construction and electrolyte type. It can be important for the controller to be able to validate the quality of the connection prior to delivering energy into the body.
Arrays of electrodes are used to acquire signals from the body surface in electrophysiological monitoring. Depending on the anatomical location of the electrodes and the signals they are intended to monitor, there can be very significant differences in signal processing parameters. For example an Electro-cardiographs (ECG) signal recovered from the chest has very different signal amplitude and spectral characteristics compared to an Electro-myograph (EMG) signal recorded from the arm.
Even within the various lead configurations of an ECG there are wide ranges of acceptable signal parameters. A multipurpose controller capable of interfacing with a range of such garments would have to have input data which allows it to process signals detected on its input terminals. This data could be input by the user however this would be tedious and error prone.
Garments may easily be configured with other signal monitoring sensors, such as temperature, pressure, force, acceleration, displacement. Insofar as these signals need to be processed by the controller, input data is required which identifies the signal type, the amplifier gain and filter pass bands required to acquire them, as well as normal limits for the signal. Such setup data could be entered by the user, however again this is not a user friendly solution.
There is a need therefore for electronic modules to automatically configure themselves depending on what garment type they are connected to. There have been some attempts to solve related problems in the past. Bastyr, U.S. Pat. No. 5,487,759 described a brace which incorporated electrodes for treating the knee. It featured a keyed connector which, in effect, implemented a 3 bit binary code to enable a controller to select which one of a selection of carrier frequencies to use. Different carrier frequencies were required for the different electrode sizes that would occur in different garments. Bastyr does not recognise any type of automatic garment recognition to enable definition of the performance of the controller.
Further and significant problems with the Bastyr solution, include the fact that solution is limited to only 3 encoding bits. Also the controller is pre-programmed to deliver one out of 8 possible carrier frequencies which were encoded to the device when it was manufactured and this creates another problem. If an additional garment were to be introduced to the range at some later time, which needed a carrier frequency not included as one of the pre-defined set, then it would be necessary to produce a new controller with updated carrier frequencies. This is because the 3 bit code merely identifies the brace and does not provide the actual treatment parameters which the controller has to use with that brace. The code was not re-writable so the configuration could not be changed.
Furthermore Bastyr has described a stimulation system which includes two channels of stimulation each of which is hardwired to a dedicated pair of lead wires and electrodes. This uses biphasic stimulation in which current flows in one direction between electrodes of a pair for a period and then flows in the opposite direction between the same pair for a period. There is no requirement to re-configure the electrical connection of the electrodes depending on the target garment, or the selected treatment for a target garment. Nor is there any consideration of the requirement to specify and store information on electrode area, electrode impedance or wear out profiles.
A partial solution to this problem is to allow the user select the target garment from a menu provided on the controller. Again this is error prone and also inflexible in that it requires that all the necessary data has been previously loaded into the controller.
It could therefore be helpful to provide a system which overcomes at least some of the problems of the prior art.
It could also be helpful to provide a system which allows a suitably programmed electronic controller to interface to a range of body worn wired garments and to recognise which garment type is connected, to select the appropriate connections to direct electrical signals to the appropriate combination of electrodes for the intended treatment with that garment, and to select the treatment timing and other parameters so that it can synthesize the necessary signals on the appropriate terminals.
It could still further be helpful to provide a system which allows a suitably programmed electronic controller to interface to a range of body worn wired garments and to recognise which garment type is connected, to select the appropriate connections for detection of specific biological signals and to apply signal processing steps appropriate to the signal type and intended use.